Installing Nest E Heat Link

13 Feb 2021
Reaction score
United Kingdom
Hi everyone, I’be never posted on here before but I’m looking for some advice.

I currently have a Siemens RDJ10RF wireless thermostat which communicates with a Siemens RCR10/433-GB. The latter is wired to the boiler with a red and black wire to L and N respectively and brown wire to L1 and Blue wire to LX and a yellow/green wire. (See pic)

I’m looking to replace this with a Nest E so will have to replace the box connected to the boiler with the heat link e. I know the heat link e is battery operated so I know I won’t need the L and N feed but I’m a little confused with the other 3 wires. The options for the heat link e are labelled C, NO, FP, OT1 and OT2.

Any help would be greatly appreciated.


  • F206E95D-A692-4855-BC3D-FE17CEE7DF11.jpeg
    262.4 KB · Views: 332
Sponsored Links
As you have figured, Nest-e is battery operated so doesn't need a 230V supply to power it. Therefore the L & N wires are not required and should be insulated / isolated and tucked safely out of the way. Do not connect them to Nest-e

Then the wires presently in the Siemens LX and L1 simply move to Nest-e terminals that have exactly the same function as follows:

Siemens LX = Nest-e C (Common)
Siemens L1 = Nest-e NO (Normally open)

Nothing should be connected to FP, OT1 or OT2.

I can't see the green / yellow wire in your photo.
Last edited:
Brilliant, thanks for your help. You can’t quite see it in the photo but there is an earth wire just behind the brown and blue wires but I can’t see what that is connected to. Is there somewhere for that to go on the Nest E Heat Link?
Sometimes a green/yellow wire is used for a purpose other than an earth. If it's not connected to anything at the Siemens don't connect it to the Nest-e. Isolate it and tuck it out of the way. Both the Siemens and Nest-e are double insulated and do not require an earth connection.

If it is connected to one of the terminals at the Siemens post back the details.
Sponsored Links

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local